Fish association and utilisation of estuarine habitats across differing levels of human impact in the Thames

Wanda Bodnar
Queen Mary University of London (QMUL)
Institute of Zoology (IoZ) / Zoological Society of London (ZSL)
University College London (UCL)

Abstract Example habitats Interactive map

Abstract

Estuarine ecosystems support some of the most biologically productive intertidal habitats, sustaining diverse fish communities through complex food webs and connectivity. However, human-induced pressures, including urbanisation, degradation, and climate change, threaten the ecological integrity of these habitats. The Thames Estuary (UK) has experienced significant historic habitat loss, impacting fish populations and ecosystem resilience. Although ongoing intertidal habitat creation and restoration efforts aim to address these issues, the ecological functions of these habitats remain insufficiently understood. This study seeks to fill this knowledge gap by investigating how fish utilise created (or engineered) and restored intertidal habitats, examining their trophic interactions, and assessing the role of connectivity in maintaining estuarine ecosystem function.

A multidisciplinary approach integrating traditional net-based sampling, environmental DNA (eDNA) analysis (including gut content metabarcoding/metagenomics), stable isotope analysis, and functional guild assessments will be used to evaluate species diversity, diet composition, and habitat quality. Environmental variables including salinity, temperature, turbidity and dissolved oxygen are incorporated to explore how physicochemical gradients and habitat characteristics influence fish distribution, foraging behaviour, trophic dynamics, and ecosystem functioning.

The findings will provide valuable insights to inform evidence-based restoration strategies, ensuring that habitat interventions enhance ecological resilience and sustain fish populations while improving connectivity in the Thames Estuary.

Example habitats

Stanford-le-Hope - Restored (Lower Thames Estuary)

Point Wharf - Created/Engineered (Middle Thames Estuary)

West Thurrock - Degraded (Middle Thames Estuary)

Syon Park - Natural (Upper Thames Estuary)

Interactive map

In 2025, sampling took place in June and will be repeated in September/October at 22 sites across the Thames Estuary. These sites represent a range of intertidal habitat types — including created/engineered, restored, natural, and degraded areas.

The interactive map below shows the location of each site, the associated habitat condition, and the water sampling points used for DNA analysis. Blue markers also display site photos in a popup window.